A mouse-clicked helper button keeps focus, so the next Enter re-fires it instead of confirming

Fact

Most browsers focus a <button> when it is clicked with the mouse; Safari does not, by design. A page that confirms with Enter, and correctly leaves Enter on a focused button to that button's native activation, therefore sends the next Enter to whatever helper the user last clicked — a +1/−1 stepper, a hint toggle — instead of to the confirm action.

Why it matters

The confirm path works in keyboard-only testing and in Safari, and breaks only after a mouse interaction with a secondary control. The symptom reads as a logic bug ("Enter adds one more degree", "Enter hides the hint") rather than as focus sitting somewhere unexpected.

How to apply

• For controls that adjust something the user then confirms, call preventDefault() on their mousedown: focus stays where it was, the click still fires, and keyboard users can still Tab to the control.
• Or move focus back to the primary control at the end of the helper's action.
• Test the sequence "click helper, then press Enter" with real input, not a dispatched click: a synthetic click() never moves focus.

Related: [[key-event-runs-two-steps]].